Hi now that you've created your first app 
let's take a first look at some of the basic hardware and software concepts 
hardware refers to the computers electronic and mechanical components 
such as it's chips and it's disk drive 
and in flash drive keyboard etc 
software are the programs or code that control the hardware 
so for example your I have a dream app control the Speaker of the 
device and it told it to play the recording a model is our king 
general-purpose computers are computers that can run any program we give it 
so for now you've given the device theme 
our Luther King app 
but you're going to be writing lots of other apps in this course 
we contrast general-purpose computers with special-purpose computers 
these are ones that have fixed programs that can't be changed such as a watch or 
a calculator program or the anti-lock braking system in your car 
the computer programmers a person like you who designs and write software 
in fact that will be you in a few weeks 
Let's take a closer look at hardware 
now the main hardware components are showing this functional diagram 
first of all is the memory : 
this is temporary memory and this is where your program is stored while it's running on the device 
the central processing unit is the brains of the computer that it's the unit that interprets each of your 
programs instructions and tells the other components on the computer to carry them out. 
for example when you want to play a sound,
it tells the sound component to play the sound that you give it.
The hard drive is the permanent storage device. 
Here's where your apps and your sounds and your pictures are stored permanently 
even when the power is off. 
The last functional component are the various input and output devices 
that connect to our computers. 
For example on the smart phone, there is the touch screen, the mic, the speakers and so forth.
All of these devices are connected to the computer through its motherboard 
which is a printed circuit board that houses all of component.
This is a picture of the Sony Playstation motherboard.
the chip in the middle here is the central processing unit for the Sony Playstation.
A chip is an integrated circuit that contains millions of tiny electronic circuits and devices. 
we also have other chips on here such as the memory chips 
and chips that control the i/o devices that can be attached to the computer.
Here's a closer look at a chip. don't be misled by the size the chip itself is a very tiny 
rectangle in the middle that has millions of diodes and switches and circuits on it. 
if you opened up your Nexus phone you'd find a similar motherboard pointed out here is the 2 
gigabyte memory chip 2 gigabytes is 2 billion bytes that's about 2 billion characters
Underneath it which you can't see directly is a central processing unit. 
ut there's other chips on this motherboard as well 
for example 1 outlined in purple here is the audio chip this controls the sound component 
when you tell it to play the speech by Martin Luther King 
and the modem component controls its communication 
with the Internet you turn the motherboard around you'll find fill 
other components the 8 gigabyte flash drive is for permanently storing your 
apps and your music and your pictures 
8 gigabytes is 8 billion bytes or 8 billion characters 
and you also have chips for the phone for communicating with the internet 
the HDMI chip is for displaying high-definition output on your touchscreen 
so those are some of the main hardware components and concepts 

let's now take a look at software. 
Software serves as an interface between us and our computers 
so in this case the interface consisted of some buttons that you put on it and some labels 
and when you touch the button it would play the right sound now apps are just one part of the interface between 
us and our computers between the application layer where the I have a 
dream app reside and the hardware layer 
this is the operating system 
in our cases the Android operating 
system this contains a lot of software 
that helps us use our devices for 
example when we want to load an app the 
operating system has a piece of software 
called an app loader and when we tell it 
to take a picture it has a piece of 
software that controls the camera and 
another that controls the touchscreen 
all of the software has been written by 
programmers and it makes our ability to 
use our devices much much easier it 
would be the same picture if you had an 
iPhone the only difference would be that 
it would be using the iOS operating 
system the reason we need all this 
software to interface with our computers 
is because they can only understand 
their own language by this I mean Apple 
machine language or Nexus machine 
language or Samsung machine language 
that explains why you can't run an 
iPhone app on your Android device and 
vice versa unfortunately we don't have 
to program in binary code computer 
scientists have created lots of 
high-level languages that are readable 
by humans but of course in order to run 
on the computer or on a smartphone the 
high level programs have to be 
translated into machine language by 
special software called translator 
software it translates the high-level 
program which is called source code in 
the liberal level binary code it may be 
useful to step back for a moment and 
think about the fact that these 
languages are really abstractions that 
help us deal with our computers App 
Inventor is a very high-level human 
readable abstraction it lets us deal 
with the computer in terms of things 
like sound components and buttons and 
labels it gives us instructions for 
manipulating these components but 
machine language is also an abstraction 
it deals with the computer in terms of 
very low-level constructs like the 
computer's memory or the processor it 
has instructions that say things like 
load this byte of data from the memory 
into the processor or send us piece of 
data to the speaker which of course 
would play a sound because it too is an 
abstraction programs written in machine 
language have to be interpreted before 
they can be accessed 
- processor this happens at a very low 
level and we'll look at that process in 
that in a future lesson the important 
point for now is that all of these 
languages whether they be high level or 
low level are abstractions that provides 
constructs and instruction sets that led 
us as programmers deal with the computer 
itself but focus now on what happens 
when we run an app we now know that our 
I have a dream app has to be translated 
into machine language and then the 
previous tutorials you learn two ways to 
do this one by using the connect to 
companion menu the other by using the 
package and you let's talk about the 
differences between these two late when 
you click on connect your companion the 
app that you're writing on your browser 
has to be transferred over and the 
software that does that for us is a MIT 
companion app which resides on our phone 
so that takes the blocks and interprets 
them for the Android operating system 
which in turn interprets them and loads 
them into the processor and run again 
when you press a button I have a dream 
speech okay nice part about pre connect 
presenting options is that as we make 
changes on the browser's they are 
immediately interpreted and run on our 
device this form of translation where 
instructions are interpreted one by one 
immediately executed is known as 
interpretation what about when you say 
package an app well you know again that 
some kind of translation has to occur 
but exactly what it's actually quite 
different in this case in this case a 
piece of software on the MIT server 
translates your entire program into 
binary code and puts it into a file 
called an apk file if you say Falcon 
then we load it onto the phone using a 
barcode scanner or some other piece of 
software this form of translation is 
known as compilation where the entire 
source code program is translated into a 
single binary file the advantage of 
compilation is that the translation has 
to happen 
so the translation is more efficient 
however the advantage of interpretation 
is that it allows us to more easily see 
how each instruction works and to debug 
our apps as we're developing them we'll 
learn a lot more about these two ways of 
translating as we develop more apps phew 
that was a lot of new content we'll have 
more to say about some of these concepts 
in future lessons to help you review the 
terms and concepts we prepared a little 
matching activities so pause the video 
here and try matching each of the 
technical terms in the left column with 
description in the right hand column 
thank you